Apparatus for lithographing strip metal



Nov. 17, 1931. c. POWERS ET AL APPARATUS FOR LITHOGRAPHING STRIP METAL Filed Oct. 51. 1929 INVENTOR V Qm 'Paw-MA BY E W: x. Qmw PM 613% M ATTORNEYA Patented Nov. '17, 1931 UNITED STATES PATENT OFFICE APPARATUS FOR LITHOGRAPHING STRIP METAL Application filed October 31, 1929. Serial No. 403,885.

Strip metal is purchased and used for a large variety of purposes, and due to the fact that'it can be handled in substantially continuous lengths, its cost is very low. In connection with many of the uses to which strip metal is put, it would be highly desirable to have the metal ornamented, as for example, by providing stripes that run along its length, either at the sides or elsewhere, or by providing characters or designs on the face of the metal. If desired, such characters may be in the form of letters to serve as advertising. However, the processes heretofore developed for printing or ornamenting other types of material .will not serve with strip metal, and as far as we are aware no commercial product of this nature has ever been put on the market.

In considering this problem, it must be borne in mind: first, that the metal is nonabsorptive so the ornamentation must be applied sharply and truly without any slip; second, that commercial stri metal is substantially never really straig t, but has appreciable lateral bends; and third, that it is not feasible to grip the'metal after it has been ornamented until opportunity has been afforded for it to dry.

After analyzing these difficulties we have eventually discovered that strip metal can be ornamented cheaply and efiiciently either with continuous stripes or with separated characters, or both, by moving the metal under appreciable tension at a' predetermined rate of speed and contacting the metal with a transfer roll (to which the ink has been properly applied) which rotates at exactly the same peripheral speed as the tensioned metal. In order to feed the metal at the definite speed and keep it under tension, the strip is passed between a pair of rolls in advance of the printing station, which are positively to pull the metal from the source of supply, but grip the strip tightly enough so that the tensloning means cannot pull it any faster than the peripheral speed of these rolls. In other words, these rolls serve the double function of feeding the metal and also of checking its speed; whether the sum of these opposite forces is negative or positwo will, of course, depend upon the strain exerted by the tensioning means and the drag necessary to ull the metal from the source of supply. he gearing for these rolls should be so arranged as to take care of either 68 state of affairs with a minimum of play and the transfer roll should be directly connected w1th these rolls through gears so that the all will maintain the same peri heral spee The tensioning means should e capable of causing the metal to move at a substantially faster speed than that permitted by the feed control rolls, but must exert an im ositive pull on the metal which will yield be ore the metal starts to slip at the feed control rolls. We have found that this can advantageously be accomplished by maintaining the entire strip under tension until approximately the wind-up point, and there winding the metal I through the medium of a friction drive. If desired, some of the pull on the winder can be taken up by passing the metal around drums or pulleys which themselves are impositively driven through a friction drive.

By the arrangements described. the chance 76 for slip between the metal and the transfer roll is eliminated and the metal is kept in correct alignment, for the relatively heavy tension kept on the metal will counteract the errors that would otherwise be caused 80 either by lateral curves in the strip or by inequalities in gauge which might tend to create a side throw.

As regards drying, we have found that the metal can be caused to traverse a long path between grooved pulleys which contact with the edge of the strip, and if these paths are horizontal the sags that occur serve as an added factor in equalizing the tension maint ained against the feed control rolls. If the friction drive at the wind-up exerts too reat a tension the sags will successively be s ortened with an accompanying increase of pull on the grooved pulleys which can ordinarily be noted and corrected before too great a strain is exerted on the feed control rolls. In like manner, if the friction drive becomes too light the winding may stop or slow up, but the sags of the metal wil increase in size so that tension is maintained. In fact,

with such an arrangement, the friction drive could be eliminated from direct combination with the feed control rolls, for if asecond pair of rolls positively driven at the same speed as the feed control rolls were provided to grip the metal as it leaves the drying zone, the pull at the sags would exert an impositive pull on the metal tending to remove it from the feed control rolls faster than they would permit, so that the necessary tension would be maintained.

Our invention may be readily understood by reference to the accompanying drawing, which shows somewhat diagrammatically a side elevation of an illustrative machine with which our invention may be carried on.

In the drawing, 12 is a reel on which the metal strip is placed. The metal strip M is here shownas passing from the reel 12 around the V-grooved pulley 14 and going between the pair of feed control rolls 16, which grip the strip firmly to prevent slipping. The feed control rolls 16 are driven by appropriate gears directly from the pair of rolls 18 and 20 in such a way that the metal will move between these latter two rolls at exactly their peripheral speed. Of these two rolls, roll 18 is a backing roll and roll 20 the transfer or printing roll. Following the usual custom of offset printing, the transfer roll receives ink from the type roll 22. The ink is contained in a reservoir 24 in which rotates inking roll 26. Roll 28 intermittently touches roll 26 and then travels to roll 30 where it deposits a small amount of ink. This ink is spread out by oscillating motion of rolls 32 and 34 which operate in a manner well known in the art. The ink which has been spread out on roll 30 is transferred to the tvpe roll 22 by the inking rolls 36 and 38. Inasmuch as the metal is to be printed continuously, the transfer roll 20 is made with continuous surface. If desired, adjustable guide rolls 40 may be provided to assist in keeping the metal strip in line with the transfer roll, though for this purpose we must rely primarily upon the tension kept on the metal, which pulls against the feed control rolls.

The necessary tension on the metal is applied at or near the winders. but before reaching this point the strip ordinarily has to be dried. Thus when the metal leaves the printing station, it passes over a V- grooved pulley 42 (so that only the slde edges of the strip are in contact with the pulley) and then it is run back and forth over a series of pullevs 44 and 46 arranged in the furnace- 48. It is to be understood that the numerals 44 and 46 indicate two rows of pulleys arranged side by side on a common shaft and that as many pulleys may be used in each series as may be necessary to give the proper time for drying. These rows are spaced apart a substantial distance so that there is a sag in the metal at each span.

When the metal leaves the furnace or drying oven, it may be passed around the cooling drums 49 and 50. These drums are driven through a friction drive, not here illustrated in detail, which tends to give them a periph: eral speed greater than that of feed control rolls 16, but which slip so that such speed will average the same as that of the feed control rolls. Temporary variations are unimportant, provided the average is maintained, for the variations will be taken care of by increases or decreases in the sags between the rows of pulleys 44 and 46.

From the drum 50 the metal passes to a winding reel 52 which is driven by a friction drive which is preferably set to slip more readily than the drive of drums 48 and 50 so that as the metal collects on the reel and the effective diameter increases, this drive will slip, and the metal will be wound up at the speed permitted by the movement of drums 49 and 50. If preferred, the drums 49 and 50 could be eliminated or allowed to run as idlers, and all of the tension could be maintained from the friction drive of the winding reel 52.

By the arrangements described and shown, ordinary commercial strip metal can be ornamented both rapidly and cheaply, and it is to be understood that by the words ornamenting or printing we intend to include the application of stripes or symbols or both, of a nature which contrasts with the background or body color of the metal. In like manner, the word ink is used for the purposes of illustration, and is not intended to impose a limitation on the nature or consistency of the substance used for forming the ornamentation.

What we claim is:

1. In an apparatus for ornamenting strip metal, feed control means for feeding the metal at a predetermined rate of speed, means for exerting an impositive pull on the metal tending to remove it from such feeding control means at a greater rate of speed than such feed control means will permit, whereby the metal is maintained under tension, a printing roll adapted to contact with the tensioned metal. and means whereby the peripheral speed of the printing roll is maintained equal to the speed of movement of the metal.

2. In a mechanism for continuously printing strip metal. the combination of a pair of feed control rolls adapted to grip a strip of metal to cause the same to move at the peripheral speed of such rolls, a printing roll adapted to contact with the metal after it leaves said pair of rolls, means for driving said printing roll, means for causing said pair of feed control rolls and said printing roll to rotate at the same peripheral'speed, and means for maintaining an impositive pull on the metal after it has been contacted by the printing roll, whereby the metal is maintained under tension while in contact with the printing roll.

3. A mechanism as specified in claim 2 in which the means for maintaining such impositive pull comprises a rotary member around which the metal is adapted to pass and friction means tending to drive such 10 member at a greater peripheral speed than that of the feed control rolls.

4. The method of ornamenting strip metal which comprises moving a strip of metal continuously at a predetermined speed and under 15 substantial tension and contacting such strip of metal while under such tension with a printing roll rotated at the same peripheral speed as the speed of the metal.

5. The method of ornamenting strip metal In which comprises the steps of feeding the metal continuouslyfind positively into contact with a printing r 11, causing such roll to rotate with a peripheral speed equal to the speed of movement of the metal and main- 25 taining a yielding tension on the metal tending to keep it straight under the printing 11. m csnmc POWERS.

. BAYARD M. CRUM. 

